Apparatus for contact arc suppression in an electric generator regulator



Feb. 28, 1956 c. w. KLUG 2,735,357

APPARATUS FOR CONTACT ARC SUPPRESSION IN AN ELECTRIC GENERATOR REGULATOR Filed May 1, 1953 2 Sheets-Sheet l J0 Z ADMATURE CURRENT IN AMDERES VOLTS "PEAK ACROSS CONTACTS b Feb. 28, 1956 c. w.

APPARATUS FOR CONTACT ARC SUPPRESSION IN AN ELECTRIC GENERATOR REGULATOR 2 Sheets-Sheet 2 Filed M 1 953 Iiz K is? Char/e United amass-7 APPARATUS FOR CGNTA CT ARK: SUPPRESSION IN AN ELECTRIC GENERATOR REGULATOR Charies W. King, Chicago, iii.

Application May 1, 1953, Serial No. 352,346

6 Claims. (Cl. 32269) This invention relates to an apparatus for contact arc suppression and more particularly to a method and apparatus for contact arc suppression in which the resistance connected across a pair of contacts to suppress arcs is changed during operation of a circuit to achieve maximum suppression of the arcs.

Where a pair of contacts are in circuit with an energy storage device such as an inductance, the energy stored by the device will be discharged in the form of an arc across the contacts when the contacts are opened. This has been the cause of severe difiiculty in the past due to excessive pitting of the contacts, erosion and sometimes actual welding of the contacts.

it is possible to reduce the contact arcing by providing a resistance across the energy storage device to absorb part of the energy. This method has the disadvantage, however, of increasing the current flow through the contact thus partly, if not entirely, obviating the eifect of the absorption of the energy.

If the circuit need not be completely opened upon opening of the contacts, a resistor may be connected across the contacts to absorb energy and reduce the arcing. In any such case, however, there is a limit on the lowest possible resistance which may be connected across the contact without causing real-operation of the circuit.

It has been discovered that in many circuits the limit on what the lowest value of resistance across the contacts can be without causing mal-operation of the circuit varies during the operation of the circuit.

A good example is in voltage and current regulators used for limiting the output of a battery-charging generator, such as those used extensively in automobiles. In such regulators it is usual to provide relays actuated by the voltage across and/ or the current supplied from the generator, the contacts of these relays being in series with the field of the generator. When the voltage and/ or current exceed predetermined values, the relay contacts are opened to reduce field current. In normal operation,

the relay contacts will be vibrating between open and closed positions and the percentage of the time that the contacts are closed is automatically controlled so as to limit voltage and current of the generator to optimum values.

For arc suppression it is, of course, desirable to have the lowest possible resistance across the contacts. However, the lowest possible resistance which may be connected across the contacts without causing mal-operation of the circuit varies during operation.

In accordance with a specific feature of this invention, the value of the resistance across the voltage and current relay contacts of a voltage regulator such as described above is changed in accordance with operating conditions so as to achieve maximum absorption of the energy stored in the generator field so as to thereby eliminate excessive contact arcing and pitting.

By another feature of this invention, the resistance across the contacts is changed in accordance with field current, which,--it has been found, is very sensitive tO-ClICUltCOI'idles Patent Cir 2,736,857 Patented Feb. 28, 19 56 ice tions. This is preferably accomplished by a relay actuated in accordance with field current to connect a low resistance across the voltage and current relay contacts.

It has been discovered that in the regulator circuit as described above, the stored energy in the generator field, which energy must be dissipated when the contacts are opened, is at a maximum at the point of operation of the circuit where a very low resistance could be connected across the contacts without causing mal-functioning of the circuit while at the point of operation of the circuit where the resistance must be very high to prevent mal-operation of the circuit, the stored energy is com paratively low. This invention, accordingly, achieves an extremely high reduction in contact pitting, erosion and welding without causing any rnal-functioning of the regulator circuit.

in accordance with another important feature of this invention, a relay and resistance associated therewith are arranged in a self-contained unit which may be readily installed on the generator of an automobile to achieve the high reduction in contact arcing.

in accordance with still another specific feature of this invention, a relay is provided which is particularly adapted for use in the combination with the generator voltage and current regulator as described above. in the circuit as described above, it is essential and imperative that the low resistance should not be accidentally connected in the circuit by closing of the relay contact when the condition of operation is such that a low resistance would cause maloperation or the circuit. Since the relay is mounted on the automobile generator, a difiicult problem is presented in providing a relay which will not accidentally close with the severe jars and vibrations to which the automobile generator is subjected.

in accordance with this feature, a relay is provided with an armature which is balanced about its pivotal axis so that jars and vibrations will not eflect closing of the contacts. This relay, of course, may have generalapplication although it is peculiarly and particularly adapted for the combination with the control circuit of this invention.

An object of this invention, accordingly, is to provide improved arc suppression means and methods by which the value of a resistance connected across contacts is changed in accordance with operating conditions.

Another object of this invention to provide improved methods and means for reducing arcing at the voltage and current relay contacts of a generator voltage regulator by which the resistance across the contacts is changed in accordance with field current.

A further object of this invention is to proved balanced armature relay.

Still another object of this invention is to provide improved arc suppression apparatus for generator voltage regulators which includes a balanced armature relay.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description ta ten in conjunction with the accompanying drawings which illustrate preferred embodiments and in which:

Figure 1 is a circuit diagram of a generator voltage regulator circuit incorporating the principles of the present invention;

Figure 2 is a perspective view of an attachment for a generator having a conventional voltage regulator connected thereto, the attachment incorporating a balanced armature relay producing peculiarly advantageous results in the combination;

Figure 3 is a schematic diagram of a modified circuit according to the principles of this invention; Y

Figure 4 is a graph illustrating the operation of 21 voltprovide an image regulator system with and without the improved arc suppression means of the present invention;

Figure 5 is a top plan view of the attachment of Figure 2; and

Figure 6 is a top plan view of a regulator incorporating the arc suppression means of this invention.

While it will be understood that the arc suppression means and methods of the present invention have general application, they will, for ease of understanding, and to prevent undue prolixity, be described only in connection with a generator voltage regulator system in which they achieve particularly and peculiarly advantageous results.

Referring to Fig. 1, reference numeral 10 designates a direct current generator having an armature 11 and a field 12. One brush of the generator 11 and one end of the field 12 are connected together and to ground while the other brush of the generator 11 is connected to a terminal 13 and the other end of the field 12 is connected to a terminal 14. A voltage regulator generally designated by reference numeral 15 and having terminals 16, 17 and 18 is connected between the generator terminals 13 and 14 and a storage battery 19 having a load 19 connected thereto.

In order to better appreciate the present invention, a conventional voltage regulator circuit and its operation will first be described. In the conventional circuit, the terminal 13 of the generator would be connected directly to the terminal 16 of the voltage regulator, as is illustrated, and the terminal 14 would be connected directly to terminal 17 which is not as illustrated. The terminal 18 is connected to one terminal of the battery 19, the other terminal of the battery being connected to ground.

The terminal 16 is connected to one end of a coil 20 of a voltage relay 21, the other end of the coil 20 being connected to ground. With a predetermined current through the coil 20, an armature 22 will be moved out of engagement with a contact 23 associated therewith. The terminal 16 is also connected to one end of a coil 24 of a current relay 25 which includes an armature 26 moved out of engagement with a contact 27 with a predetermined current through the coil 24. The other end of the coil 24 is connected through a potential coil 28 of a reverse current or cut-out relay 29 to ground and also through a current coil 30 of the reverse current relay 29 to one end of an armature 31 normally in engagement with a contact 32 which is connected to the terminal 18 of the voltage regulator.

The contacting parts 22 and 23 of the voltage relay 21 are connected in series with the contacting parts 26 and 27 of the current relay 25 between the terminals 16 and 17 and hence would be connected, in the conventional system, between the armature terminal 13 and the field terminal 14. To reduce arcing, a resistor 33 is connected between the terminals 16 and 17 so as to be across the contacts 2223 and 2627 and a resistor 34 is connected from the terminal 17 to ground.

This circuit is particularly designed for use where the generator 11 is operated at a variable speed as in the case of automobiles. In operation of the conventional circuit, when the generator 11 is driven at a high enough speed, the potential across the coil 28 of the reverse current relay 29 is sutficient to close the contacting parts 31 and 32 to connect the battery 19 through the coil 24 of the current relay 25 to the generator armature 11. In a higher range of speeds, and with relatively low loads on the battery 19, the current through the coil 24 of the current relay 25 and the voltage across the coil 20 of the voltage relay 21 are not sutficient to open the contacts 2223 or 2627 and the field 12 of the generator would be connected directly to the armature terminals of the generator. When either the charging current applied through coil 24 of the current relay 25 or the generator output voltage applied to the coil 20 of the voltage relay 21 reach high enough values, the contacts 2627 or the 4 contacts 2223 are opened so as to reduce the current through the field 12.

When the current through the field 12 is reduced, the output voltage of the generator is reduced and the potential across the voltage relay coil 20 and the current through the current relay coil 24 are reduced so that whichever one of the contacts 2223 or 2627 was opened is then closed to again connect the field 12 across the armature 11 of the generator 10. The field current will then be increased thus increasing the generator output and the potential across voltage relay coil 20 and the current through current relay coil 24 so as to again open one of the contacts 2223 or 2627. The cycle is then repeated over and over and the regulator operates to automatically control the percentage of time that the contacts 2223 or 2627 are closed and the average field current so as to limit the generator output voltage and the current to the battery 19 and load 19' to safe values. In a typical regulator, the maximum charging current is 35 amperes and the maximum regulated voltage is 7.5 volts.

The resistors 33 and 34 are provided to absorb and dissipate the inductive energy in the field 12 when either of the contacts 2223 or 26-27 is open and thus decrease arcing at the contacts. The values of these resistors 33 and 34 are determined by design considerations. The resistor 34 is in series with the contacts 2223 and 2627 and hence increases the current flow through these contacts as Well as increasing the load on the generator. This resistance 34 must, accordingly, be large enough so as not to cause excessive current through the contacts 2223 or 2627 or excessive load on the generator.

While it would be desirable for suppressing arcs across the contacts 2223 and 2627, to have the resistance of the resistor 33 as low as possible, the resistance must be high enough to limit the field current to a low value when contacts 2223 or 2627 are open so that the voltage output of the generator will not be excessive at high speeds and low loads.

In a typical conventional regulator, the resistor 33 has a resistance of 21 ohms and the resistor 34 has a resistance of 14 ohms.

According to this invention, the resistance across the contacts 2223 and 2627 is reduced when the operating condition of the circuit is such that a low resistance can be connected across the contacts without causing mal-operation of the circuit. This is herein accomplished by a relay 35 having a coil 36 connected between the terminals 14 and 17 in series with the field 12. When the average current flowing through the field 12 reaches a predetermined value, an armature 37 is pulled into engagement with a contact 38 and a resistor 39 is connected between the terminals 16 and 17 and across the series connected contacts 2223 and 2627 to thereby reduce the resistance across those contacts. The resistor 39, of course, aids greatly in absorbing the stored energy of the field 12 when the contacts 2223 or 2627 are open and thus greatly reduces arcing at the contacts. At the same time, voltage regulation is maintained since with field current above a predetermined value, a comparatively low resistance may be connected across the contacts 2223 and 2627 without causing excessive field current and generator voltage.

It may be noted that when the relay 35 is energized and the contacts 37--38 closed, the current through the coil 36 is increased during the time when contacts 2223 or 2627 are opened to thereby increase the average current through the coil 36. This serves to provide a holding or locking-in function to prevent the possibility of vibration of the armature 37 in synchronism with armatures 22 and 26. a

In a typical regulator, such as the regulator 15 as described, it has been found the optimum operation is obtained with the relay 31 operating at an average field current of approximately 1.1 amperes and with a resistor 39 having a value of ohms.

While it is now apparent that this arrangement will substantially reduce arcing at the contacts, it has been discovered that a much greater reduction is effected than would be expected. This, it has been found, is due to the fact that the arcing at the contacts becomes greater as the field current increases since the stored energy which must be dissipated at each opening of the contacts is greatly increased as field current is increased. By this invention, accordingly, a low resistance is connected across the contacts when the conditions of operation of the circuit are such that arcing would normally be very high. Thus, an extremely high reduction in arcing at the contacts is achieved.

Figure 4 is a graph illustrating the operation of the arc suppression means of this invention and was obtained with a voltage regulator such as above described with a standard automobile generator 10 driven at a substantially constant speed of approximately 2500 R. P. M. In this graph, the peak voltage across the contacts 22-23 and 2627, that is, the voltage between the terminals 16 and 17, is plotted against the generator armature current. Line 40 in this graph illustrates the operation without the arc suppression means of this invention connected, that is, with the terminal 14 connected directly to the terminal 17. It will be observed that with low loads, the peak voltage across the contacts is comparatively low, the voltage across the contacts being increased as the armature current is increased.

Now with the arc suppression means of this invention connected, that is, with the relay 35 and resistor 39 connected as illustrated in Figure 1, the contacts 3738 will be closed and the resistor 39 connected across the contacts 2223 and 26-27 when the field current through the coil 36 reaches a predetermined value. With the conditions of operation such as above described, this will take place with armature current somewhere in the range between 5 and 10 amperes and the operation with higher armature current will be as represented by line 41 in Figure 4. It is apparent that the peak voltage across the contacts and hence the arcing at the contacts is sharply and greatly reduced.

Figure 3 illustrates another preferred arrangement in which a relay 42 has a coil 43 which, like the coil 36 in Figure l, is connected between the terminals 14 and 17. This relay 42 has a special armature and contact arrangement with an armature 44 arranged to engage a contact 45 and with a leaf spring 46 secured at one end to the armature 44 and arranged to engage a contact 47. With a predetermined field current through the coil 43, the spring 46 will be engaged with the contact 47 to connect a resistor 43 between the terminals 16 and 17. The resistor 48 may have the same value as the resistor 39 in the circuit of Figure 1. This resistor 48 will, of course, greatly reduce arcing at the contacts connected between the terminals 16 and 17.

When the average field current through the coil 43 reaches a higher value, the armature 4 4 will be engaged with the contact 45 with the spring 46 flexing to allow this additional movement and a resistor 49 will be connected between the terminal 16 and the terminal 17 in parallel with the resistor 48 to further reduce arcing at the contacts.

The operation of the modified arrangement of Figure 3 is also illustrated in Figure 4. With an armature current of about amperes, the field current through the coil 43 will be such as to engage the armature 44 with the contact 45 and with higher armature currents, the operation will be along line 50 in Figure 4, the operation with lower armature current being the same as described above in connection with the circuit of Figure 1.

It will be apparent that the arrangement of Figure 3 may be further extended to obtain additional stages of operation or, if desired, additional relays may be provided to have multi-stage operation.

Figures 2 and 5 are perspective and top plan views, respectively, of an attachment for conventional automotive generators which incorporates a balanced armature relay, according to further features of this invention. This attachment comprises a base 51 which should be of an insulating material with an angle bracket 52 secured to the under side of the base 51 and arranged to be bolted to the armature terminal of a generator and with a plate 53 secured under the opposite side of the base 51 and arranged to be bolted to the field terminal of a conventional generator. Also mounted on the base 51 are a relay 54 and the resistor 55 arranged for connection in a generator voltage regulator circuit in a manner like the relay 35 and the resistor 39 in the schematic diagram of Figure 1.

The relay 54 comprises a generally L-shaped bracket having an upstanding leg 57 and a horizontal leg 58 which is secured against the base 51. The upstanding leg 57 is centrally recessed at its upper end to provide a pair of integral side lugs 59 and 60. An armature 61 rests on the upstanding leg 57 and is recessed to receive the lugs 59 and 60. The recesses in the armature 61 are slightly greater in size than the lugs 59 and so that the armature has limited pivotal movement about a horizontal axis.

A coil 62 having a magnetic core (not shown) is mounted on the horizontal leg 58 of the bracket 56 and acts magnetically on the right side of the armature 61. A spring 63 connected between the armature and the upstanding leg 57 opposes the magnetic attraction of the coil 62. To limit the pivotal movement of the armature 61, a plate 64 of non-magnetic material is disposed over the coil 62 and has an end portion 65 turned over the right end of the armature 61.

A generally U-shaped bracket 66 has a lower leg 67 secured against the base 51 and an upper leg 68 extending over the left end of the armature 61. The left end of the armature 61 engages the leg 68 of the bracket 66 when the current through the coil 62 is sulficient to attract the armature against the action of the spring 63. Suitable contacting parts such as silvered contacts are preferably afiixed to the armature 61 and the leg 68.

The bracket 66 is connected to one end of the resistor 55 while the other end of the rwistor 55 is connected to the bracket 52 through a plate 69. One end of the coil 62 is connected through a wire 70 to the plate 53 as shown in Figure 5, while the other end of the coil 62 is connected to a plate 71 aflixed below the base 51 and arranged to be connected to a lead wire extending to a conventional voltage regulator utilized in connection with the generator on which the attachment is fixed.

A feature of this construction is the fact that the attachment can be readily and quickly secured to a generator and connected in circuit with the regulator associated therewith so as to serve the suppress arcing of the contacts of the voltage regulator.

Another feature of the construction is the fact the armature 61 is balanced about the pivotal axis thereof. In any relay installation, it is desirable that shocks and vibrations should not cause accidental opening or closing of the relay. In the arc suppression circuit of this invention, it is essential that the relay should not close accidentally particularly when the generator is operated at high speed or where there is a high load, or both, since under such conditions if the relay should accidentally close, regulation will be lost and the voltage output of the generator will be excessive which might result in severe and permanent damage to the circuit components.

With the balanced armature construction of the relay above described, the inertia of the armature is balanced 12,-mew

about the pivotal axis thereof and shocks or vibrations will act equally on both sides of the armature so that it cannot pivot about its axis except when actuated. Thus the relay is particularly and peculiarly advantageous in the arc suppression circuit of this invention and especially when used with a voltage regulator system for the generator of an automotive vehicle which, of course, is subject to severe shocks and vibrations.

While one preferred embodiment of the arc suppression means of this invention may take the form of the attachment for conventional regulators, as is illustrated and described, it will be apparent that the invention is not limited thereto and that, for example, an entire regulator may be constructed combining the arc suppression means of this invention in the same housing with other regulator components to form an integral part thereof. One such construction is illustrated in Figure 6, in which the voltage regulator relay 21; the current regulator relay 25, the reverse current relay 29 and the arc suppression means including the relay 35 are all mounted on a single base 72 with a cover 73 thereover, terminals 74, 75 and 76, affixed to the base 72 being provided to connect the regulator in circuit with the automobile generator and battery.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. In an automobile, in combination, a generator having a field, contacts for intermittently energizing said field, a resistor, and a relay including an armature balanced about a pivotal axis, spring means urging said armature in one direction about said axis, electromagnetic means responsive to field current for urging said armature in a reverse direction, and contact means for limiting mechanical movement of said armature in said reverse direction and arranged for electrically connecting said resistor in circuit with said field.

2. In an automobile, in combination, a generator having a field, contacts for intermittently energizing said field, a resistor, and a relay including an armature movable about a pivotal axis, spring means urging said armature in one direction about said axis, electro-magnetic means responsive to field current for urging said armature in a reverse direction, and contact means for limiting mechanical movement of said armature in said reverse direction and arranged for electrically connecting said resistor in circuit with said field.

3. In an automobile voltage regulator system for a generator having an exciting field winding, including vibrating contacts connected in series with the generator field winding to control generator output voltage, arc-suppressing resistance means adapted to be connected across said vibrating contacts, and means responsive to current through the field winding arranged to connect said resistance means across said vibrating contacts when the current through the field winding exceeds a certain value and arranged to keep said resistance means connected across said vibrating contacts until current through the field winding drops due to a change in generator speedload operating conditions.

4. In an automobile voltage regulator system for a generator having an exciting field winding, including vibrating contacts connected in series with the generator field winding to control generator output voltage, first and second arc-suppressing resistance means adapted to be connected across said vibrating contacts, and means responsive to current through the field Winding arranged to connect said first resistance means across said vibrating contacts when the current through the field winding exceeds a first certain value and arranged to keep said first resistance means connected across said vibrating contacts until current through the field winding drops due to a change in generator speed load operating conditions, said field current responsive means being arranged to connect said second resistance means across said vibrating contacts when the current through the field winding exceeds a second certain value and arranged to keep said second resistance means connected across said vibrating contacts until current through the field Winding drops due to a change in generator speed-load operating conditions.

5. An attachment for automobile generators controlled by a vibrating contact type voltage regulator, comprising: a first terminal for connection to an armature terminal of the generator, a second terminal for connection to a field terminal of the generator, a third terminal for connection to a voltage regulator lead which would normally be connected to said field terminal, a resistor, and a relay having a coil connected between said second and third terminals and having contacts connected in series with said resistor between said first terminal and one of said second and third terminals.

6. An attachment for automobile generators controlled by avibrating contact type voltage regulator, comprising: a first terminal constructed and arranged for connection to an armature terminal of the generator, at second terminal constructed and arranged for connection to a field terminal of the generator, a third terminal constructed and arranged for connection to a voltage regulator lead which would normally be connected to said field terminal, a resistor, and a relay having a coil connected between said second and third terminals and having contacts connected in series with said resistor between said first terminal and one of said second and third terminals.

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